JPS61242303A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To use flying erasion heads exclusive for forward and reverse modes respectively and to obtain the satisfactory erasion characteristics, by providing an erasion circuit which has the 1st and 2nd modes for recording video and sound signals and switches the erasion currents flowed to the 1st and 2nd rotary erasion heads in each mode. CONSTITUTION:A recording track is divided into six parts, i.e., CH1-CH6 successively from the lower side of a magnetic tape 1. Then the PCM sound signal is recorded to each divided area. In this system the CH1, for example,is recorded forward as shown by an arrow head 2. While the CH2 can be recorded reverse as shown by an arrow head 6. The track width TW' of a flying erasion head is set double or more as much as a track pitch PT(TW'>=2PT) so that this erasion head can erase two tracks at a time. As shown by 4a, the preceding erasion head erases the areas equivalent to tracks 3a and 3b before these tracks are recorded by a video head. The following two tracks 3c and 3d are also erased and recorded in the same way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a recording circuit for a helical scan household magnetic recording/reproducing device (hereinafter referred to as a VTR), and particularly relates to a recording circuit for a helical scan type household magnetic recording/reproducing device (hereinafter referred to as a VTR), and in particular for recording a magnetic tape without using a full-width erase head. The present invention relates to a magnetic recording/reproducing device having an erasing circuit that enables erasing.

[Background of the invention]

In conventional home VTRs, there is a system in which the full-width erase head is removed and a 7-line erase head is provided separately from the recording/reproducing magnetic head to improve the performance of editing functions such as splicing and inserting. For example, JP-A-5
Japanese Patent Application No. 9-42606 reports a means for realizing erasing in a two-head VTR by using a single flying eraser having a track width twice or more than the track pitch.

In addition, for example, in Japanese Patent Application Laid-open No. 58-222402, the recording track is divided into several parts, and each area has, for example, a
Although a system for recording audio signals converted into commercials has been reported, no specific method for erasing recorded tracks in the system has been reported so far.

Currently, in addition to the standard recording mode, 4-head VTRs have a long-time recording mode, and FM-modulated audio signals are recorded on the video track using an audio head mounted on a cylinder, achieving high sound quality. Six-head type VTRs have also been commercialized, and when systems using flying erase heads are considered, the number of heads tends to increase more and more.

[Purpose of the invention]

An object of the present invention is to solve the above-mentioned problems and erase a PCM audio signal recorded on a magnetic tape (hereinafter abbreviated as PCM audio signal) without using a full-width erasing head.
To provide a flying erase method capable of recording M audio signals in both forward and reverse tape feeding directions.

[Summary of the invention]

In the present invention, the recording track is divided into 6 areas, and each area has PCM.
For VTRs that can record audio signals in both forward and reverse tape feed directions, they have a dedicated flying erase head in both forward and reverse modes, and are mounted on a rotating cylinder so that sufficient erasing characteristics can be obtained. defines the location and provides the cancellation amplifier configuration.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG. 1st
The figure shows a recording pattern viewed from the magnetic surface on a magnetic tape. As shown in the figure, the recording track is divided into six, and the magnetic tape 1 is divided into six parts, CHI, CH2, ..., CH.
This system in which IcPcM audio signals are recorded in each area of 6 is hereinafter referred to as a multi-channel PCM system.

In this system, each channel records and plays independently, so
For example, record CHI in the forward direction as shown by arrow 2, and
It is also possible to record H2 in the opposite direction as shown by arrow 6. Furthermore, regarding erasing, it is necessary to erase each CH separately, and here, erasing using a flying erase head will be explained.

First, the 0 flying erase head, which explains erasing and recording when the magnetic tape runs in the forward direction, is 2
1The track width T is set so that the tracks can be erased at the same time.
w' is more than twice the track pitch PT (Tw'≧2PT
) (as shown in 4a, the video head is on track 3a.

Before recording track 3b, the preceding erase head records track 3.
Erasing and recording are similarly performed for the zero-order two tracks 3c and 3d, which erase areas corresponding to areas a and 3b.

FIG. 2 shows the positional relationship between the cylinder and the video head attached to it. 10 is the upper cylinder, 1
5 is the lower cylinder, 16 is the rotational direction of the cylinder, 11 is the video head, 13 and 14 are the lower and upper surfaces thereof, and 12 is the helad gap. As is well known, when the magnetic tape 1 runs in the forward direction 2, as shown by CHI in FIG. 1, arrows 5a, 5b, 5c.

The position of 5d is determined by the lower surface 13 of the head 11, and in the opposite direction 6
When the magnetic tape 1 is running at
It is determined by the upper surface 14 of 1. Therefore, in order to prevent the flying erase head from erasing newly recorded tracks, in the forward direction 2, that is, CHI, the lower surface of the flying erase head should be aligned with the arrow 5a as shown by 4a and 4b.
, It is necessary to attach it to the cylinder so that it is aligned with the position 5c. Similarly in the reverse direction 6, i.e. CH2, 8a,
As shown by 8b, it is necessary to install the flying erase method so that the upper surface thereof is aligned with the positions of arrows 9a and 9c.

The track width T W/ of the flying erase head is T
If w'≧2PT (PT is the track pitch), it is impossible to align the flying erase head in two directions, 2 in the forward direction and 6 in the reverse direction, as described above.
Therefore, two flying erase heads are required, one for the forward direction and the other for the reverse direction.

FIG. 3 is a diagram showing the installation of the head in a two-head VTR, in which (a) shows the head arrangement on the cylinder;
b) shows the difference in level between the bottom of the spatula. 17 is a cylinder, 18.
20 is a video head, 20 is a forward-direction-only flying erase head, and 21 is a reverse-direction-only flying erase head. Here, track pitch PT Ka20
Track width Tw of μm1 video head 18.19 is 20
A case is shown in which the μm 7/F in-erasure head 20.21 is mounted offset by θ=900 with respect to the video head 18.19. Considering PT=20μm1θ=900,
Flying erase head 2 for forward direction only as shown in (b)
The bottom surface of 0 is 10 μm from the bottom surface of video head 18.19
Similarly, the upper surface of the 7-line erase head 21 dedicated to the reverse direction is 10 μm higher than the upper surface of the video head 18.
It is sufficient to add a step difference ΔH shown by . Generally, ΔH is P T
It can be expressed using N θ.

In addition, the track pitch in a mode in which the magnetic tape operates at a standard tape speed V (standard recording mode, hereinafter referred to as SP-[needle]) is changed to a mode in which the magnetic tape operates at a speed of PTIN (n is an integer) (long-term recording mode, hereinafter referred to as SP-[need)]. The track pitch in the LP mode (referred to as LP mode) is assumed to be PT2.

At this time, the level difference in which ΔH is determined by the PT value in the SP mode becomes too large, but the newly recorded track is not erased. On the other hand, if ΔH is moved to LP mode, the difference in level is too small in the SP mode, and the newly recorded track will be erased, which is inconvenient. Therefore, the step difference ΔH needs to be a value determined from equation (1) using the track pitch PTI in the SP mode.

Next, using FIG. 4, a method for installing a head in a four-head VTR will be explained. FIG. 4(a) shows the head arrangement on the cylinder, and FIG. 4(b) shows the level difference between the heads. 24 is the cylinder, 25.26 is the LP head, 27.28 is the SP head, 29 is the 7 line erase head for forward direction only, 3
0 is a 7-line erase head exclusively for the reverse direction.As shown in the diagram, θ1 and θ2 are 60° and 1200, respectively.
Let the track width of the SP head be TWIN, the track width of the LP head be TW2, the track pitch in SP mode be PTI, and the track pitch in LP mode be PT2. From formula (1), if ΔH for the SP head and LP head are ΔH1 and ΔH2, PTI nPT2 ΔHx = −=□ ・・・・・・・・・・・・ (2
)PT2 ΔH2=□ ・・・・・・・・・・・・ (3)
becomes. The track width TWI N TW2 is limited from a performance standpoint in a normal 4-head VTR: PTI≦TWI≦1.5 P T 1 - ... -
-(4) PT2≦TW2≦1.5 PT2 --
−・” (5). Also, as shown in Figure 4, S
In order to install the P head 27 (28) and the LP head 25 (26) so that they coincide at the track center, the SP head 2
The lower surface (upper surface) of 7 (28) is the LP head TWI.
It is lower (higher) than the lower surface (upper surface) of TW2 25 (26). Here, flying erase head 29
(30) is set based on the bottom surface of the LP head 25 (26). At this time, the bottom surface (top surface) of the SP head 27 (28) and the flying erase head 29 (30)
The lower surface (upper surface) of

From equations (4) and (5), the minimum value is TWI”
PTI = nPT2, Tw2 = 1.5 Since n is an integer greater than 2 at PT20, the following holds true. Therefore, it is only necessary to attach the ΔH2 glaze head 29 (30) based on the LP head.

The values in Figure 4(b) are TWI = 20 μm, T
W2=15 μm.

This is when PT1=20 ttm and PT2=10 pm, and in this case ΔH2=6.7 μm.

As mentioned above, in a 4-head type VTR, the LP head, SP head, and flying erase head are arranged at 60 degree intervals with respect to the cylinder rotation direction, and the flying erase head is attached to the LP. Erasing is possible in both forward and reverse directions.

Next, we will introduce a 4-head VTR using a double azimuth head.
The case will be explained using FIGS. 5 and 6. A double azimuth head is one in which two heads having seven different azimuth angles are arranged close to each other (0.5H to several H, where H is the horizontal scanning period). In FIG. 5(a), 35 is a cylinder, 36.37 is an SP head with +azimuth and -azimuth (hereinafter referred to as SP 10 head, sp-
38.39 is an LP head with -azimuth and +azimuth (hereinafter referred to as LP-head and LP-10 head), 4.0 is a forward-only flying erase head, and 41 is a reverse-direction flying erase head. It is an erase head.

Heads 36, 38 and 37, 39 are double azimuth heads, and the gap distance is close to 0.5H to several H. Figure 5(b) shows the step difference between each head. and
The SP heads 36, 37 and LP heads 38, 39 are mounted so that their track centers coincide. The track width of the SP head 36 (37) and LP head 38 (39) is TW1% TW2, and the track pitch is PTl.
Let's call it PT2. Also, flying erase head 40,
41 is θ(
The gap distance between 36, 38 and 37.39 is sufficiently smaller than θ and can be ignored. ), if installed as far away as
From equation (1), there is a constant relationship here with respect to SP heads 36 and 37. Also, video head 36, 37, 38.
39 has the same track center, so the SP head 36 (37), LP head 38 (39), and 36 (37) are higher. Here, if θ=900, then from equation (1) S
If ΔH for the P head and LP head are ΔH1 and ΔH2, then the following equations are obtained. Also, a feature of a 4-head VTR using a double azimuth head is field still (steal is performed using the same azimuth head) in both SP and LP modes, and therefore adjacent interference in the LP mode (from a point of view). T
WI≦2PT2. Also, considering the LP performance, P
There is a relationship of T2≦TW2≦1.5PT2. Therefore, SP
A step difference ΔH1 with respect to the head 36 will be added to the seven line erase head 40 (41). At this time, LP
Head 38 (39) and flying erase head 40 (
Since n is an integer larger than 2 according to equation (8), the step difference ΔH2' from the flying erase head 40 (41) is as follows.In the LP mode, the flying erase head 40 (41) does not erase the newly recorded recording track.

Therefore, a 4-head V using a double azimuth head
In the TR, by attaching the 7-line erase head 40, 41 at θ=90° as shown in Fig. 5(a), and using the sp head 36 (37) as shown in Fig. 5(b), it is possible to erase in the forward and reverse directions. When a magnetic tape is running, erasing is possible in both SP and LP modes. Δ[1=10 in FIG. 5(b)
μm is TWI=20pm-, TW2=1! yμm
This is an example when s PTI = 20 μm and PT2 = 10 μm.

Figure 6 is a special case of Figure 5, where 'rwt = 20
μms TW2 = 15μm, PTI = 20μ
When m −s PT 2 =10 μm, θ=45
By setting ΔH1, the step difference is 4 as shown in Fig. 6(b).
As 7.48, it becomes equal to ΔH1ΔH, and SP, LP
In both modes, recorded tracks can be completely erased.

Next, a second embodiment of the present invention will be described using FIGS. 7 and 8. As explained in Figures 3 to 6, different flying erases are used in the forward and reverse directions to change the level difference, so if the erase current is applied to both 7-line erase heads at the same time, a new In order to erase the recorded track, it is necessary to switch the erase current between the forward and reverse directions.

Figure 7 shows an example using two erasure amplifiers 55 and 56.
FIG. 8 shows an example using one erase lamp 67. 7th
In the figure, 55, 57, and 59 indicate an erase amplifier, a rotary transformer, and a flying erase head exclusively for the forward direction, and 56, 58, and 60 indicate an erase amplifier, a rotary transformer, and an erase head exclusively for the reverse direction. The erase signal is switched by the switch 50, and the recording/reproduction discrimination signal (RFC), the CH switching signal (CH) shown in FIG. The timing chart is shown in FIG. 9. When playing (RI
C) The signal goes low and switch 50 is connected to b. When recording (RFC) signal becomes high level and (CM
) signal is always at a high level, indicating the recording period of the video signal, and Ihl always flows to the head 59 in the forward direction (there is no reverse direction recording with respect to recording of the video signal). (Switch 5
0 is connected to a) The signal (A) is 3 0 H made from the tack pulse, which is phase information sent from the rotating cylinder.
For example, when recording CHI in the forward direction as shown in FIG.
The level becomes high at the position corresponding to HI, and the forward head 5
Engineering hl flows on 9th. (Switch 50 is connected to a) Next, when recording CH2 in the reverse direction, the (F/R) signal becomes high level, the (CH) signal becomes high level at the position corresponding to CH2, and the reverse direction head 60 Ih2 flows.

(The switch 50 is connected to C.) FIG. 8 shows an example in which the forward and reverse erase currents Ih, , Ih2 are applied by the switch 68 on the output side of the erase amplifier 67, and the erase signal 0N10FFK is This is done by the switch 62 at the front stage of the erase amplifier 67. During reproduction, the switch 62 is connected to the b side, and no erase signal is sent.

FIG. 10 shows a specific example of the erase current switching circuit shown in FIG. 74 is an erase signal input terminal, and 75 is an input terminal for a signal (REC.CH) which is an inversion of the addition signal (RFC-CH) of the (RFC) signal and the (CH) signal. (RFC
-CH) becomes low level, transistor QIK bias is applied and the erase signal inputted from 74 is transmitted to the subsequent circuit. Further, when the (F/R) signal is at a high level, the transistor Q3 is turned on and an erase current flows through the forward head 72, and when the (F/R) signal is at a low level, the transistor Q4 is turned on and an erase signal flows through the reverse head 73.

Ll is for turning on Q3 or Q4,
It is necessary to set the inductance sufficiently larger than the inductance of the heads 72 and 73. Further, the capacitors C2 and C3 form a resonant circuit together with the head 72.73, and the rotary transformer 70.7
The effect of reducing the effective power supplied to the stator side of
:be.

Figure 11 shows the four-head type VTR shown in Figures 4 to 6.
This figure shows how to connect the rotary transformer and the head. 77 shows a cross section of the core of the rotary transformer. In order to eliminate crosstalk interference during recording from the flying erase head to the video head, grooves 7, 8.
A flying erase head is arranged at 79, and grooves 81 to 84
By arranging the video head between the two and inserting a short ring into the groove 80 between them, crosstalk interference can be avoided and the number of grooves can be minimized.

〔Effect of the invention〕

According to the present invention, in a system for recording and reproducing video signals and multi-channel PCM, when recording is performed by running a magnetic tape in the forward and reverse directions, recording tracks can be completely erased in both directions. Along with
Erasing systems for 2-head VTRs and 4-head VTRs having both 5PSLP modes can be realized with a minimum number of flying erase heads.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a recording format of an embodiment of the present invention;
Fig. 2 is a diagram showing the operation of the cylinder and magnetic tape, Figs. 3, 4, 5, and 6 are diagrams showing the structure of the head on the cylinder and the vertical relationship of the heads, Figs. 8 is a circuit diagram of the erasing circuit, FIG. 9 is a timing chart, FIG. 10 is a specific circuit diagram of the erasing circuit, and FIG. 11 is a sectional view of the rotary transformer. Explanation of codes 20.21.29.30, 40, 41.45.46.5
9.60.72.73...Flying erase head, 55.56.57...Erasure amplifier, 50.62.68...・Switch circuit, 77...Rotary transformer core 1 Leap 2 Kaku 5 Figure 6 Figure 6 (β) Go (4') 3 Figure (shi) 4 Figure

Claims (1)

[Claims] A helical scan type magnetic recording and reproducing device having at least two magnetic heads mounted on a rotating cylinder, which has a first mode for recording video signals and several recording areas on a magnetic tape in the scanning direction of the magnetic heads. and a second mode in which a PCM audio signal is recorded in each of the divided magnetic tapes, and in the second mode, recording is possible in the forward and reverse running directions of the magnetic tape, and A first rotary erasing head is provided on the rotating cylinder for a forward mode and a second mode, and a second rotating erasing head is provided on the rotating cylinder for a reverse mode of the second mode. What is claimed is: 1. A magnetic recording/reproducing device comprising: an erase circuit having one erase circuit in each of the rotary erase heads and switching erase current flowing through the first and second rotary erase heads according to the mode.